The present invention relates to a semiconductor integrated circuit having a battery control function and an operation method thereof, and particularly to a technology effective in making it possible to shorten the time taken to calculate a full charge capacity Qmax and an internal resistance value being parameters related to deterioration of a battery.
Portable equipment for consumer use such as a notebook personal computer (hereinafter referred to as “note PC”), a cellular phone, a smart phone or the like needs to notify battery's characteristic information about the degree of deterioration of a secondary battery used as a power supply, the remaining capacity and time of the battery at its discharge, or the remaining capacity and time thereof at its charge, or the like to a user.
The following Patent Document 1 has described that a remaining capacity SOCc based on current integration in which charging and discharging currents of a battery are integrated, and a remaining capacity SOCv based on an estimated value of an open voltage of the battery are weighted to calculate a combined remaining capacity SOC. Further, a current capacity change rate σ is calculated from a change ΔSOCc in the remaining capacity based on the current integration and a change ΔSOC in the combined remaining capacity. When the current capacity change rate σ reaches a predetermined value or less, it is determined that the deterioration of the battery has occurred. Incidentally, the remaining capacity (SOC) is called a charge rate or a state of charge.
The following Patent Document 2 has described a method of determining the deterioration of a battery using a state of charge (SOC) calculated by integrating charging and discharging currents of the battery. A current-based state of charge (ISOC) is generated from the charging and discharging currents of the battery, and a voltage-based state of charge (VSOC) is calculated from the voltage of the battery. When the value of either of them is high, the current-based state of charge (ISOC) is subtracted from the voltage-based state of charge (VSOC). When the subtracted value exceeds a first threshold value or when the subtracted value is less than a second threshold value where the value of either of the two is low, an additional value is added to a deterioration coefficient to modify the deterioration coefficient. When the deterioration coefficient exceeds a third threshold value, it is determined that the battery has been deteriorated.
The following Patent Document 3 has described a method of performing an arithmetic operation on a charging time up to the end of charge where a secondary battery is charged by constant current/voltage charge. An open voltage for the secondary battery is detected. A constant current charging time is calculated from the open voltage and a voltage drop developed across an internal resistance of the secondary battery at the constant current charge. A constant voltage charging time is calculated from a voltage drop developed across the internal resistance. Then, a charging time taken up to the end of its charge is arithmetically operated from the two.
The following Patent Document 4 has described a method of calculating a relative remaining capacity of a secondary battery and a full charge capacity thereof. First, a relative remaining capacity SOCfull is calculated from a reference table in accordance with an open circuit voltage OCVfull in the fully charged state of the secondary battery. Thereafter, a relative remaining capacity SOC determined from the reference table in accordance with an open circuit voltage OCV detected upon the stop of discharge of the secondary battery is corrected based on the relative remaining capacity SOCfull in the fully charged state, whereby a true relative remaining capacity SOCtrue is determined. Further, a discharging current of the secondary battery is integrated to determine a discharge capacity Q [Ah] from the fully charged state of the secondary battery to its discharge stop. A full charge capacity Qfull of the secondary battery is determined as Qfull=Q÷[(100−SOCtrue)/100] based on the discharge capacity Q and the true relative remaining capacity SOCtrue. A method of calculating the full charge capacity Qfull is however a general method.